Dampening apparatus and method for lithographic printing



July 29, 1952 w G, MULLEN 2,604,848

DAMPENING APPARATUS AND METHOD FOR LITHOGRAPHIC PRINTING Filed April 3,1948 4 Sheets-Sheet l I Z z/rzz or G. ffa llerz 16 d4: 4 J74 A fig/1sJuly 29, 1952 w. G. MULLEN 2,604,848

DAMPENING APPARATUS AND METHOD FOR LITHOGRAPHIC PRINTING 4 Sheets-SheetP,

Filed April 3. 1948 ho'emiof Gf alleiz y 1952 w. G. MULLEN 2,604,848

DAMPENING APPARATUS AND METHOD FOR LITHOGRAPHIC PRINTING Filed April 3,1948 4 Sheds-Sheet 3 July 29, 1952 w. ca. MULLEN 2,504,848

DAMPENING APPARATUS AND METHOD FOR LITHOGRAPHIC PRINTING Filed April 3,1948 4 Sheets-Sheet 4 Patented July 29, 1952 V f JiDAMPENINGF'APPARATUSAND 43K :LIEHO GRAPHIC :P INTIING IWill iam G iMu len;Winchester,"'Mas s., assign, 'iby mesne assignments, tOI'Ai B.'-=Dick-Gompany,

village of-Niles;* Ill.,'acorporationmf Illinois epnlicat o Apri -h c Ii1$,3.

. x1 ,..Thi s invention-relates chinefor-lithographic printing.

. EAILfOI'mS, of lithographic printing embody. the use, of a printingplate having inkereceptive areas and "water-receptive, ink=rep ellent,no-neprinting a ea aandiitis well neco nized that ,i-nvorderto tion,of,theink andfdampening solution. p o lllce Satisfactory printing .stheanon-printing .eAlfiifthen ,cli'fliCllliiYfiMi'ibutfiMe te aw f la nareas must be maintained-:sufiicientlyrmoistto f eri'.blanket is,theflqimensional *cha ee w d repehtheink a p ied to ther r ntin plate.H-Actortionoithejshecti nsin d r fii m cordinslyy it is n ess yrte-apply at: least peri- 1O inQiStnre i trans crrcd to its'tsi e from ithe di l y n aqueous rliquidrorI-solution '(hereinblanketmpairticularlyin regis r W K- after referred?,to ,as --Water) stothe: surface,- ofvtheAlthou h nume o s at mpts :haveh et m printing :lplate, and .to this.end it. p is time usual heemmadeto avoidih above-menti d pr c i t mp1.oya so-called Mo1leton; roller vantacesflso' :aras g m wa l a mrwhichmomprisesc.ansabsorptive fabric surface haveiiailed 4100providva:reliablranrkefilcicht having a .direct contact with.thenqprinting; plate method .of accurately controllingj theramqunt-ofso astolapply to 1 itssur face; a. ifilm of water. water applied; tofthe iprintine-ipla enand m I :iswellknown-that if,-.an excess-amountedtheildamnenin s stcmiof"a f'li eraphic pr n water-sis. applied-andpermitted to remain on :the ins .machin s, Stil ,lf lnfifill -i al i Pprinting tplate -it-has a-tenden ytQ-interfere with 1cm. .theink-receptivity of the printing-areas sandliThenpl'incipal'Qlgiects'pfffthe -presentfim ention emulsifying (withthe printing ink, consequently arewto piicmirle an efficientyandreliable methed producing-la grayTandi-indistihct print. Onthearena.machine i ndampcnin t efpr n flthernhandeif insufiicienbwater-is-:app1icd 1'00 of a lithographic printingpfrnachine which aremaintain the non-printing areaseinkerepellent, notzsubjecttqtheaforementionegifdimcultiesand they become ,fouledawith p-inkianclconsequently produce- 1 a :dirty or, smuclgy print, necessitatingcleaning, the vprinting plate: whichqis; an irksome, time-consuming,pmcedure greatly interfering wit production. uDue tov the;absorbentchanacterrofsthe surface .of; the roller, it, iS,3-practical;1yimpossible 1 I not 7 .only accurately, to control the amountmf waterapplied to thanprintineg plate, but; also therevennessr of vthe :waterafilrn anci the k-rpe1 ha a i rof .tha intin a ea rare reli acn lely cimi-nat i-meisture.irom thes parts. p

; -Moreover,-..- since the' MolletQn :01" wetting;- roller 20111651111direct :contactwith .theyprintlng plate, it inotaonlyz tends .to pickupvinkcandethusbecome dirty, requiring :-frequent -,'c1e anir 1g andperiodic, replacement of its, absorbent: covering, ,lqiit-zalsov causes:an appreciable wear ;on-.the,vsurface: of t the. printing; plate which;ultimately impairs ,both the; printing and non-printingeareas,

to-amethod. of K antima-- most cnateqpapersgare more orlessalkalinegthepresencelof a small m untni such at ne mav terialilends not onlytQQpSetthqDI-N da pni solution, but 8i1dfj0jlPIOVidfiliflrefifietfanemulsifying a ent which prqmotes-emnlsiiicadisadyantages; .to vproyide;a clampeningfsystem which may; be attached o aplilied toconventionalspresse r.flbcthzthe'zqfisetiand "direct typ and: to;both-sheet, and web, ypr sses .and-t royidea damn nia s s em wit ass c ad c tmlswhioh" is relatively-inexpen iv mmanuiw ture, install andoperate 7 ;.Eurth.er obj cts wi 'lqeapp r ntirom;a--considerationnpflihemllow ll f'QQSQ l Pfi n': en he mpan n drawil snw erein- E leis, a;-schematic, view'rq a f f set pr ss. e u pped.. withihamamnenin systsmemb g l thepresentinyentiqn; v j I v Eicwzis aschemati ivie.w.otawehfifisetPms 'embodyinemyi amnen nasystcm i" -z-F'ia,,verticalgsectionali elevaticnOil-1asheet.rpressihavina!a.,.damnemnc.sxstemis nlilar LtolimatinustratedmErie;;

:rEig 4 fislaitop, plan iewrnflthe thusredncing theli f ofthe plate.-When itrris e-Eig; is. awiWmf t1,=ie=.iend,,.of;the. wate iiifl desiredtmchange from one colonize-another; it iand-assqciateq plate cylinderQPPQSLBQIILQBTSQQWQ is -necessary,; in order to avoid contaminatiomtochange: the Molleton roller. and in soine cases the water-transfer.rolls associated.therewith.- Such a procedure is' time-consuming,requiring the usual trialvrunsaduring WhiOhtthBT necessa yre- 34 3'ustments must be made.

Another rdiificulty encolmtered -in offset presses embodying aconventional "dampening f system when; printing. or-;coated; papersisthe: tendency on the coatinamaterial. or other chemicals con- :tained-;therein to zwork orl- -ber carried ;back"- by riwayrovfetherwettransferzhlanketnonto:Vthe;print- .inggplateandinto-theaampeninasoilution. *2 Since loft,

I g. 26 Dis ant enlal edafiectionalisometric' view lcr. .inwhichftheiairlnez e. ada'nstablnmountedrandr I'l-iislansisometric.sziewro ithcssupmtiec -Mackstiontheldamnenii ys1lem.

I'n,acco1tdance withithepresent inyentienf' hflisappliedstoc-the.surfacevofsallithq "p. 11 militinc p atehavin .-,iha11s11alsinkvxeqcptivc irintin areasandrwatehreceptive ncneprintinlarea ia .centinuousrfilm f water.ionm istenin isolutiqn inscxcessapfthat requinedion prpnenmo stetl ll the,mom-printing.areaswarterrwnichgal,rclae with tively high velocity jet ofair or other gas is directed/against the moistened surface of theprinting plate at an angle efiective to remove substantially all waterfrom the printing areas and simultaneously reduce the thickness of thefilm of water in the non-printing areas to a minimum required forrepelling ink therefrom. A greasy lithographic ink may then be appliedto the printing plate in the usual manner and the ink film thus appliedmay then be transferred either to the offset blanket or directly to thesheet to be printed. The lithographic plate or surface may be of stone,metal, a hydrophilic colloid or any other material having lithographicproperties, and the continuous film of water is preferably applied by aroller maintained in closely spaced relation to the surface of the plateor other means which does not come in actual contact with the printingplate. The air jet should be in the form of an elongate blade extendingacross the plate, or at least the area which has been wet, and directedat such an angle as is effective cleanly to brush off all water from theprinting areas and simultaneously sweep back the excess water from thenon-printing areas. The effectiveness of the air jet may be varied byadjusting the distance of the nozzle and/or its angular positionrelative to the printing plate and/or by varying the air pressure for agiven setting of the air nozzle. In any event the velocity and angle ofthe jet should be such as to hold or brush back the excess moisture fromthe nonprinting areas andsweep away all water from the printing areas,without causing abrasion or impairment of the surface of the plate.Since the velocity and position of the air jet are subject to preciseadjustment, an accurate control of the moisture remaining on thenon-printing areas may be secured.

If desired, after inking the moistened plate, but before transfer of theink film, a jet of hot air may be directed against the plate so as toevaporate a substantial portionof the water remaining in thenon-printingareas, thus partially drying out the non-printing areas so that noappreciable moisture is transferred to the surface of the sheet to beprinted. .An illustrative application of my improved dampening system toan offset press is schematically shown in Fig. 1, wherein the numeralsI, 2 and 3 designate the plate cylinder, blanket cylinder and impressioncylinder, respectively. The blanket cylinder 2 is preferably offset,relative to vertical line through the axis of the cylinder I, so as toprovide space for the dampening system. and except ashereinafter noted,all parts of the press are of conventionaldesign and' construction.

The cylinder I carries the usual lithographic printing plate 4 which maybe of metal, parchment, gelatin, casein or other colloid-coated fibrousmaterial or the like, the plate 4 extending about the cylinder I withits ends 5 and 6 secured in spaced relation to each other inconventional manner. Between the ends 5 and 6 the cylinder I is formedwith a depression extending theentire length of the cylinder into whichis fitted a shallow scoop 8 of generally arcuate cross-section. Theusual inking rolls I0 are provided at the top of the cylinder totransfer ink from a reservoir .(not shown) to the face of the printingplate 4.

[At the underside of the cylinder I is a water transfer roll I I whichis preferably rubber covered .and'disposed in'approximately tangentialrelation to the printing'plate 4. Each end of this rollis rotatablysupported in a bearing carried by the depending arm of a bell crank I2pivoted at It to the frame of the press so that the roll II dips into atrough I5 which carries water or moistening solution, the constructionand arrangement of parts being such that the roll Il may be moved towardand away from the cylinder I and printing plate 4. A tension spring I6connected with the depending arm of bell crank I2 urges the roll I Itoward the plate cylinder I, and an adjusting screw l8 carried by thedepending arm and engageable with a lug I9 carried by the frame limitsthe inward movement of the roll so that any desired degree of adjustmentof the water roll relative to the printing plate 4 may be obtained. Theroll II is preferably driven at approximately the same peripheral speedas the printing plate 4 and may be independently driven in any suitablemanner, or, as here shown, may be connected with the plate cylinder by aloose fitting crossed belt or chain I! which permits the roll II to beswung toward and away from the plate cylinder sufficiently to move theroll to and from operative position.

Although the water roll may be brought and maintained in direct contactwith the printing plate 4, for the reasons above pointed out it ispreferable to maintain a spacing between the roll II and surface of theprinting plate of the order of a few thousandths of an inch so thatwater picked up by the roll II will span the gap and thus be transferredto the printing plate in the form of a continuous film somewhat inexcess of the amount required for proper moistening of the plate. A gapor spacing of approximately 0.003 inch has been found quite satisfactoryin that such a spacing is less than the thickness of the film or waterlayer picked up by the roll II and there is little danger of the rollcoming in direct contact withthe plate 4 when properly attached to thecylinder I.

The upper arm of each bell crank is associated with a cam 20 carried bythe shaft supporting the cylinder I, the cam 20 being designed to swingthe bell crank clockwise, thereby swinging roll II away from thecylinder I, when the trailing end of the printing plate 4 and the scoop8 travel past the line of application of the water, thus arrestingtemporarily the application of water, but allowing the roll I I to swingback to operative position under the influence of spring I6 when theleading end 5 of the plate reaches the line of application of the water,thus resuming normal operation.

At a level preferably slightly below the horizontal plane passingthrough the axis of the cylinder I is an elongate air nozzle 25 directedat a downwardly inclined angle so as to deliver a bladelike jet ofrelatively high velocity air against the surface of the printing plate 4which, as above explained, is effective to brush back excess moisturefrom the non-printing areas and sweep away all water from the printingareas. The nozzle 25 extends across the surface of the printing plate 4and is formed with an elongate slit 26 leading from the plenum chamber28 which is connected with a suitable compressed air supply by a linetfiprovided with a control valve 3| and pressureregulating valve 32. Thesize of the nozzle 25, dimensions of the slot 26, operating pressure andother such factors will vary in accordance with the size and speed ofthe press. For example, in an offset press using conventional plates, anozzle having a delivery slot approximately 0.01 inch wide and spacedfrom the surface of the printing plate 4 a distance of 0.012 to 0.015inch, gave satisfactory results with an operating pressure in supply1ine'-38 of between one and one-half andf'five pounds gage whenoperating at: a plate-speed r of l00to 250 feet perminute. ",Whenoperating-at higher speeds a greater pressure :is :usually required-fora givensettingof the 'nozzle.

":Interposed between the rol1 II- aridihe nozzle is a pair of downwardlyinclined -bafflesz34 spaced apart a distance-slightly greatenthanathewidth of :scoop -8 and so arranged irthat as the scoop approachesthe--nozzle'i25,:the excesszwater brushed: back by: theiair- -jet--.runs z'intoz-the :scoop and -is then :blown. out by. the action 1of: :thezair Jemima-baffles being reflective not onlmtoiprevent thewaterfrom beingscatteredbut also .to :conduct it back to the troughii,*or'lelsewhere asi desired.

In operation the roll I I vpicks -up from: trough 15=and appliesto theplate 4 a continuous :film of :water, andthe jet-issuing. from the:nozzle '25 brushes the :water from-the printing areas and simultaneouslyreduces the 'filmfof-swateronithe non-printing: areas: toa minimum. Theinking *r'olls I 0 then apply-a film ofinkwhich is received by theprinting areas only, and this film is transferred to the surface of theblanket cylinder 2 andthen-to the sheets being fed-in conventionalmanner between the blanket :and impression cylinders.

Substantially the same dampening system: may be -applied'toa webpress,-as schematically illustrated in Fig. 2,- whereinflthe numerals" 4I 42 an'd -43 designate; respectively, the plate; blanketand impressioncylinders, and between the latter' two is fed in conventional manner asheet or web W to Joe-printed. f in this embodiment-the printing plateis wrapped almost completely around the cylinder- 4I;and itsends arebrought as closely together as possible-and sealed mechanically or by'acovering ofwax orthelikewater-repellent material 45 which preventsmoisture from working under the plate.

"The water roll II is driven-by--a=sm al1 backgear motor 48 mounted on aplate 50 carried 7 by thefra-me of the press; and theplate 50is-adjustablymounted; as indicated at SI, on guideways '52 so'ithatthe-roll II dipsinto trough I5; tile -parts "being-adjusted to-maintain-a =gap between the surface ofplate' 44 and roll I I ,as'inthepreviously described embodiment. A nozzle 25 and-associatedcontrols-and inking rolls- ID are provided'-as-in the previously*described embodiment, -*and between the nozzle 25 and roll 1 I I is J asingleEbalflie 34-=efiective to conduct back to the trough l5;;:orelsewhere; accumulations of water brushediback by the 'jetissuingfromnozz-le 25.

in this installatiomthe water groll' I I is at: all times in operativeposition;- and as -it is "desirous of-minimizing if not-eliminatingmoisture carried by the plate 44 at thetime of actual V printing, one-ormore drying nozzles '55 1 may" be positioned posteriorly of the inkingrolls I0 so as to-"direct oneonmore jets of air against theprintingplate, thereby evaporating. atleast a substantial portion ofthewaterinthe non-printing areas "by the'time the-ink film istransferred-"to the blanket'cylinder -12. I

TheAembOdiment I shown in Figs. 3 "to" 7 illusitrates the manner inWhi'ch the dampening sysz t-em may be built into or applied toa--conventional sheet'press having-the usualuprightframe-memdaersor-"sides- 6I and ii'lbetween which-are supportedtheplate cylinder 'fid and associated transfer cylinderand-impression-cylindez GBWhibh are ofiset relative .to the platecylinder. 'iThese *cylinders-' are driyemin conventionakmanner andto1-be -printahbetweemthe cylinders St and- 66 it being un'derstoodthat:anyef the well-k-nown feeding mechanisms maybeemployed. "The usualinking mechanism, :comprising awseries: of contiguous rolls i Iflnassociated withaan tink' reservoir 1 I "through -a :pivotallyrmountedtransfer roll I2, is "mounted between t-he frames 6 I and Bland exceptfor the hdampening system presently -..to be describ ed, theageneral-design; :construction and mode of: operation ofirthepress issubstantiaily identical" :tozthose 'of; conventional sheet presses suchas aMultilith.

iThedam-pening system; in principle: is-substantially' the-same-as .thatshown hand comprises-an elongate Ushaped-supporting bracket *;(Fi'g. "7):which is secured to :the frames --6 I and 62 sol'that itshorizontalshelf is below the plate cylinder 64- an'diin approximatetalignment withthe-axis of the blanket cy1indert65, as shown in'Fig. 3. Thai-bracket"I5 supports Y. a trough I6 which contains the"dampening solution andthe side members oithezbracket I5 carry-aligned stub shafts 'I8,-1eachof which-supports a bell cranktll. Theclowei: arm oi-eachbell crankcarries; a; bearing-in which-once end of the shaft- 8| of the water roll1.82 I isrotatably mounted and the other end of each bell :crank 1carriesa follower 84 engageable with a cam 85' fixed-torthe shaft 86supporting .thezplate cylinder 64; the :construction andarrangement ofparts-being such that-the bell-cranks normally:supportthe-rolliso thatit .dipsinto the trough 76. The plate cylinder 6 41 is pr'ovidedvwithItheusualzanchoring means for holding the opposite :ends :of theprintingplate 88 and between: the

anchoring means :the surface of:ther-cylinder is recessed toreceiveZthQ-SCOOIYQQ ESillthe embodiment of'Fig." 1.

The :design of thespartslissuch thatzthe cams :85 rotate the :bell:cranks clockwise 5 (Fig. 3) rtofiswing. the rwater rolli;82 away fromthe plate cylinder :when :the scoop-90 approaches the line ofapplication: of-the rdampening solution and :then permits the w waterroll tombesrestored to normaloperating :position $.(Fig. '53) when thescoop passesrthe line ofiapplication. Springs 9 I "connected at I oneend-i to each ":of the vertical arms of "the bell cranks and at theiropposite end to: a lug; 92- carriedi-by the-bracket "I 5' urge the armsinwardly-toward thezplate cylinder; and adjusting screws 94; arecarried: by" the "depending arms -:0f *the 'ibell cranks :and areengageable 'with: lugs'f 95 carried*bythe bracket '15 to limit theinward: movement of thewater-roll. 82 so "that it'is' normallymaintained approximately 0.003 inch? from the surface of the: printingplate 88 carried by -the :cylinder'-'64.

I The roll 82- is driven at 1 approximately the :same peripheral speedas thatpf'ithe printing pla-te 88 and-to 'this'enda sheave 96 '(Fig.-5)is :secured a to the shaft 8 6* and this sheave: drives a 'doublegroovesheave 91' carried by-one of' the "stub shafts I8 'through across beltor chain 98. "'Thesheave ==91 .drives a sheave 99 secured to the shaft8| through a' belt orchain' illll. With "this construction :and:arrangement, the

water rollmay be swung toward and away from fthe plate cylinden andstill-be continuously driven vregardless of its rposition -rrelative tothe 1 'plate justabiy supported-by *the bracket 'l-5- so as to Fig.9 3is provided withta 'partition I035 dividing the-usualieedingme'chanismfll carries thesheets ts its 'interiorf 'imozfrontrzaridrrear ksections., "The rear section is provided with adischarge opening I04 through which dampening solution flows into adischarge pipe I05 and the front section is provided with an inletopening IBIS connected with a supply pipe I68 and an opening throughwhich projects an overflow pipe III! which maintains a predeterminedlevel of dampening solution within the front section of the trough. Theoverflow pipe IE is connected with a return pipe III which leads to thereservoir I12 at the bottom part of the press between the frames GI and62. The discharge pipe MS may be connected to the, return pipe III asshown in Fig. 3, if it be desired to recover excess dampening solution,but if such excess solution is not to be re-used, then the dischargepipe'may be suitably connected with a drain so that it will not berecirculated through the system.

The lower part of the reservoir H2 is connected to a cartridge filter orthe like II which in turn is connected to the inlet of a smallcentrifugal pump H driven by a motor H6. The discharge port of the pumpH5 is connected to supply pipe lilt' which has a regulating valve I I8adapted to control the rate of flow of the damp? ening solution totrough I5. With the arrangement herein shown, excess dampening solutionis conducted by the baffles I81, I62 to the rear section of the troughand the excess solution pumped into the front section, together with theexcess dampening solution removed from the printing plate, is returnedto the reservoir, drawn through filter H4 and the filtered solution ispumped back into the front section of the trough Ii.

The upper ends of the vertical sides of bracket I5 support a fixed shaftI29 on which is mounted a pair of spaced depending arms I22, the upperends of which are formed with split sockets I25 (Fig. 6) permitting thearms to be swung in one direction or another and secured in any desiredposition of adjustment. The lower ends of the arms 122 support anelongate air nozzle I25 by means of a connection I26 which permits thenozzle to be rotated through an angle of about 90 relative to the armsI22. The nozzle I25 comprises a tubular member having a section of itswall cut away to form a longitudinally ex tending slot, and a pair ofspaced lips I36, ISI (Fig. 6) are adjustably secured at the cut-awayface so as to define a discharge opening or slot I32 extending thelength of the body portion of the nozzle. The width of the dischargeopening I32 may be varied, but as above noted it is preferably of theorder of 0.01 inch so as to discharge a blade-like relatively highvelocity jet against the surface of the plate 88.

One end of the nozzle- I25 is connected by a flexible tube I35 with anair supply line I36 leading to a source of compressed air such as acompressor I38 positioned at the lower end of the press and operated bythe motor I 16. The line I36 includes a shut-off valve Mil and apressure regulating valve I by means of which the desired operatingpressure may be controlled.

With this construction and arrangement the nozzle I25 is mounted inparallel relation to the water roll 82 and cylinder 6d and may be swungtoward and away from the cylinder and rotated relative to the supportingarms I22 to vary the angle of the air jet. As above noted, a spacing ofthe order of 0.012 inch between the outer ends of the lips I30, I3I, andthe face of the printing plate 88, when operating at a pressure withinthe nozzle of approximately 3 lbs. gage, has given satisfactory resultsfor press speeds of about 10bit. per minute, but for greater speeds anincreased operating pressure is used and in any case the jet angle andspacing may be varied to attain the most efiicient operation.

It will be noted that in each of the embodiments herein shown the waterroll, although maintained in an operative out-of-contact relation withthe printing plate, is effective to transfer a continuous film of waterto the surface of the printing plate in excess of that required forproper moistening of the non-printing areas, and. that the air jet isedective to remove all moisture from theprinting areas and reduce themoisture in the non-printing areas to a minimum necessary to insure inkrepellency.

Since the water-repellent character of the printing areas is not reliedon solely for eliminating water or dampening solution, as inconventional dampening systems, the danger of the printing ink and wateremulsifying is minimized, if not overcome, and hence there is little orno likelihood of producing grey or indistinct prints.

Since the water roll does not come in actual contact with the printingplate, there is no danger of fouling or contamination either of the rollor the dampening solution; nor is there any wear on or injury to thesurface of the printing plate. Hence, a change of colors in the ink maybe made without changing the dampening system or making the usualtime-consuming adjustments.

It will also .be noted that the amount of moisture remaining in thenon-printing areas can be accurately controlled by adjusting the waterroll and/or the air nozzle by a few simple manipulations and hence thepress may be efficiently operated at different speeds and with varioustypes of lithographic printing plates.

It will be further noted that since the possibility of contamination ofthe dampening solution is virtually eliminated, an accurate pH controlmay be readily maintained, and where, as shown in Fig. 2, an evaporationair jet is used, the transfer of ink is from a relatively dry printingplate to the blanket and hence the difiiculties attributable to inktransfer from a moist plate are minimized. Consequently a wide range ofcoated papers may be used with little danger of the coating material orother chemicals in the coated paper being carried back into themoistening trough by way of a wet transfer blanket. Moreover, bymaintaining the transfer blanket relatively dry, distortion of the paperin registration work is minimized, if not prevented.

In addition to securing an improved quality of printing, my newdampening system not only permits the use of metallic lithographicplateshaving a finer grain than would otherwise be possible, therebyincreasing the sharpness of the print, but also the use of finer screenswithout encountering the corresponding difliculties usually involved inthe use of such screens.

While I have shown and described one desirable embodiment of theinvention, it is to be .understood that this disclosure is for thepurpose of illustration and that various changes and modifications, aswell as the substitution of equivalent elements for those elements shownand described, may be made without departing vfrom the spirit and scopeof the invention as set forth in the appended claims.

I claim:

l. The method of lithographic printing which comprises moistening aprinting plate having 9; ink-receptive?printinggareas, and'waterereceptiver non printing;sareasgwithz a water: roller; out Iofcontact; with the cplatezandispaced therefrom: by an: amount to;apply: an excess;.of :water to-the surface .of ith'eplate;;directing,;a :.jet inlthe :form of' a-continuous:blade-of airacross the :printing plate --at an angle effective to removesubstantially all water from said printing areas. and re-. moving excessfromthe non-printing areas of the plate, contacting the surface of theplate with an' ink transfer roll whereby ink transfers from the rolltothe ink receptive areas of the plateand isrepelled by the wettedareas,andtransferring the rink-applied to saidi ink receptive-areas -to asheet to be printed;

21. The method ,offilithographic' printingwhich comprises; moistening aprinting; plate having ink-'receptive rintingareas and water-receptive,noneprinting areas with awater roller out of contact with' the. plateand. spaced therefrom by an amountto applyan excess .of water to the.surface ofjth'e plate, directing 'an'air jet extending-continuouslyacross and coextensive with the surface of the plate againstrsaidprinting plate at an angle effective to remove substantially all waterfrom said printing areas and simultaneously removing excess from thenon-printing areas, applyingagreasy ink to said ink-receptive areas,directing a stream of air against said printing plate to evaporate asubstantial portion of the Waterremaining in said non-:printing areas,and transferring the ink appliedtosaid ink-receptive areas toa sheet tobe printed.

3.A.printing machine comprising a support movable in a fixedpath andadapted to hold'a printing plate having ink-receptive printing areas andwater-receptive, non-printing areas, aiwatersroller out'of contact withthe plate and spaced; therefrom by an amount to apply an excess, of"water to the surface of the plate, in excess ,of that required for,proper moisteningan air doctor extending across the plate in spacedrelation therewith for directing a continuous blade of air transverselyacross the surface of the printing plate and at an angle effective toremove substantially all water from the printing areas and the excessfrom the non-printing areas of the printing plate, and means forapplying a film of ink to theink-receptive areas of the printing plate.

4. A printing machine comprising a support movable in a fixed path andadapted to hold a printing plate having ink-receptive printing areas andwater-receptive, non-printing areas, a water roller out of contact withthe plate and spaced therefrom by an amount to apply an excess of waterto the surface of the plate in excess of that required for propermoistem'ng an air doctor extending across the plate in spaced relationtherewith for directing a continuous blade of air transversely acrossthe surface of the printing plate and at an angle effective to removesubstantially all water from the printing areas and the excess from thenon-printing areas of the printing plate, means for applying a film ofink to the ink-receptive areas of the printing plate, and means fordirecting a stream of air against the inked printing plate to remove asubstantial portion of the water carried by the nonprinting areas.

5. A printing machine comprising a rotatable cylinder for holding aprinting plate having inkreceptive printing areas and water-receptive,non-printing areas, inking means for transfer- 6. 1In-.a: printing:machine; having agrotatable:

cylinder :for: holding azzprinting plate havi-n rink receptive-printingareas and water, receptivenone, printin area-s; an.:inkin :roll,arrangedib acontact the gsurfacecofthesprintingtplate?forvtransfen of."

ink; to theeprinting areas,-a water-roll coextensiv with and: normallypositioned .out ofmontact, with the plate andi'spaced :therefrom-byan;amountf-to transfer ,ajfil-m, of water in :excessof that-acquired for:'properrmoistening to :the surface of ithecpiate on:.the :cylinder, andan-air doctor' 'coextensiyewith the cylinder; for-directing: a:continuous sail. blade; at an angle .onto the surface :of the cylinder:between thewater 'rollrand' the inkinggrollxtoree move waterfromtheprintingtareas. of -;the,:plate and the excess of waterrfrom thenon-printing areas of the ;printing;plate.--v J '7; Axprinting :machine.comprising; a .cylinder:

rotatable about-a horizontalf axis andr; haying;

means-afar; holding a; printing plate 'havingrinke receptive printingareas;. aand watererecept-ive; non-printing; areas, an:. inking? rolliarranged;

above the horizontal plane-passing throughxsaiid axis; and operative totransfer a film of 5 ink to the printing :areas, a watertrough disposedbelow: saidhorizontal plane tandin: spaced parallel-relation to. saidicylindenia waten'rollout oficontact with the plate and spaced:therefrom by swan: amount: to apply excess water to the surfaceofi theplate, an air nozzlezflinterposed between said inking roll and saidwater roll for directing a continuous air knife extending across thesurface of the plate between the water roll and the inking roll in adirection to displace Water from the printing areas of the plate and todisplace excess Water from the non-printing areas of the plate, and abaflle for conducting the water removed from the printing plate awayfrom said cylinder.

8. A printing machine as set forth in claim 6, which includes mechanismfor supporting said water roll to move toward and away from saidcylinder, and cam means associated with said cylinder for operating saidmechanism periodically to move said water roll away from said cylinderto interrupt the application of water thereto.

9. A printing machine as set forth in claim 6, which includes mechanismfor supporting said water roll to move toward and away from saidcylinder, and cam means associated with said cylinder for operating saidmechanism as the trailing edge of the printing plate approaches saidwater roll to move said water roll away from said cylinder thereby tointerrupt the application of water and then to move said water roll backto operative position when the leading edge of the printing platereaches said water roll.

10. A printing machine as set forth in claim 6, which includes meansposteriorly of the inking means for directing a stream of air againstthe printing plate so as to evaporate a substantial portion of the waterremaining in the non-printmg areas.

V 11. A printing machine comprising a rotatable cylinder for holding aprinting plate having inkreceptive printing areas and water-receptive,non-printing areas, the surface of said cylinder between the positionsof the leading and trailing edges of the printing plate being recessedto provide a scoop, an inking roll'arranged to contact the surface ofthe printing plate so as to transfer a film of ink to the printingareas, a water roll arranged to apply a film of water to the surface ofthe printing plate, and an air nozzle interposed between said inkingroll and said water roll for directing an air jet against the surface ofthe printing plate at an angle efiective to remove substantially allwater from the printing areas of the printing plate and simultaneouslyreduce to a'minimum the thickness of the film of water in thenon-printing areas of the printing plate, the excess water thus removedbeing forced into said scoop as it approaches said nozzle.

12. A printing machine comprising a rotatable cylinder for holding aprinting plate having inkreceptive printing areas and water-receptive,non-printing areas, the surface of said cylinder between the positionsof the leading and trailing edges of the printing plate being recessedto provide a scoop, an inking roll arranged to contact the surface ofthe printing plate so as to transfer a film of ink to the printingareas, a water roll arranged to apply a film of water to the surface ofthe printing plate, an air nozzle interposed between said inking rolland said water roll for directing an air jet against the surface of theprinting plate at an angle effective to remove substantially all'waterfrom the printing areas of the printing plate and simultaneously reduceto a minimum the thickness of the film ofwater in the non-printing areasof the printing plate, the excess water thus removed being forced intosaid scoop as it approaches said nozzle, and meansior conducting waterfrom said scoop.

' 13. A printing machine comprising a rotatable cylinder for holding aprinting plate having inkreceptive printing areas and water-receptive,non-printing areas, the surface of said cylinder between the positionsof the leading and trailing edges of the printing plate being recessedto provide a scoop, an inking roll arranged to contact the surface ofthe printing plate so as to transfer a film of ink to the printingareas, a water roll arranged to apply a film of Water to the surface ofthe printing plate, an air nozzle interposed between said inking rolland said water roll for directing an air jet against the surface of theprinting plate at an angle effective to remove substantially all waterfrom the printing areas of the printing plate and simultaneously reduceto a minimum the thickness of the film of water in the non-printingareas of the printing plate, the excess water thus removed being forcedinto said scoop as it approaches said nozzle, and baflle means disposedadjacent to said nozzle and extending into close proximity to thesurface of said cylinder for deflecting water blown from said scoop bysaid jet away from the surface of the printing plate.

WILLIAM G. MULLEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 643,372 Cornwall Feb. 13, 19001,216,150 Mark Feb. 13, 1917 1,335,025 Pitkin Mar. 30, 1920 1,958,593Schultz May 15, 1934 2,002,815 Harrold May 28, 1935 2,139,628 Terry Dec.6, 1938 2,252,345 Johnson Aug. 12, 1941 2,335,954 Neal .4 Dec. 7, 19432,358,284 Davidson et a1. Sept. 12, 1944 2,395,151 Sodomka Feb. 19, 1946

